Moving Picture Experts Group-Dynamic Adaptive Streaming over HTTP (hereinafter, referred to as “DASH”) (MPEG-DASH) using the same HTTP as browsing of a web site as an internationally standardized moving image delivery protocol available for moving image delivery via the Internet has been known (for example, see Non-Patent Literature 1).
In the DASH, an adaptive streaming technique is implemented. In other words, a content supply side is configured to prepare a plurality of streams in which content of the same subject is included, and an image quality, an angle of view size, or the like changes according to a communication environment of the Internet serving as a path or a capability or a state of a reception side. On the other hand, the reception side can select an optimal stream according to the communication environment of the Internet, the capability or the state of the reception side, or the like among the plurality of streams prepared by the supply side and acquire and reproduce the selected optimal stream.
As described above, in the DASH, a metafile called a media presentation description (MPD) is supplied from the supply side to the reception side so that the reception side can adaptively select and acquire a stream.
An address (url information) of streaming data (media data such as audio/video/subtitle) divided into chunks is described in the MPD, and thus the reception side can access a predetermined server serving as a content supply source based on the url information and acquire and reproduce HTTP-delivered streaming data.
FIG. 1 illustrates an example of a configuration of a content supply system that delivers content in a streaming manner based on the DASH.
A content supply system 10 is configured with a content management server 11, a DASH segment streamer 12, a DASH MPD server 13, a cache server 15, and a DASH client 17.
The content management server 11 manages content supplied to the DASH client 17, generates a plurality of pieces of streaming data having different bit rates from content of the same subject, and outputs the generated streaming data to the DASH segment streamer 12. The DASH segment streamer 12 temporally divides streaming data of content into segments, holds each of the segments as a file, and notifies the DASH MPD server 13 of an address of a supply source of the files. Further, the DASH segment streamer 12 HTTP-delivers the file of the segmented streaming data in response to a request from the DASH client 17 of the reception side as an HTTP server.
The DASH MPD server 13 generates an MPD in which, for example, an address indicating a supply source of files of a plurality of pieces of segmented streaming data is described, and HTTP-delivers the MPD according to the request from the DASH client 17 of the reception side.
The cache server 15 present on the Internet caches the HTTP-delivered MPD, the file of the segmented streaming data, or the like. Then, when a request to transmit the cached MPD, the file of the cached segmented streaming data is transmitted from the DASH client 17-2 to the DASH MPD server 13 or the DASH segment streamer 12, the cached MPD or the cached segmented streaming data is HTTP-delivered to the DASH client 17-2 instead.
The DASH client 17 acquires the MPD from the DASH MPD server 13, selects a stream suitable for a current situation among a plurality of streams prepared by the DASH segment streamer 12 based on the acquired MPD, transmits a request to the DASH segment streamer 12, and receives and reproduces a file that is HTTP-delivered according to the request.